You sound like you know a bit about TI-99s, so let me ask you this: Do you have any idea why they made the lower case character set be small upper case letters instead of real lowercase like the Apple II or C64? A couple of years ago I did a Sunday morning project of inserting the Apple II font into the TI-99 ROM to run on an emulator, and other than having to shift the j's and g's up a pixel or two it worked beautifully.
The TI 990/10 DX 10 minicomputer was exactly the same. The teacher at my old school actually picked the TI990/10 over the PDP/11 because the PDP11 did not have "true descenders". The 990 didn't either but avoided the problem by having miniature capitals for lowercase.
The TI-99/4 was Uppercase only. I think the lower case font for /4A was a rush job but I don't know that for certain.
For the hobbyist playing with the machine today there are many 10s of different fonts that have been developed and it doesn't take much to load them in BASIC, Forth, C or Assembler.
